Showing papers on "Fishing published in 1995"
Book•
01 Jan 1995
TL;DR: This chapter discusses the effects of climate change on marine ecosystems, which have an impact on species invasions, introductions, and translocations, as well as management measures and factors that increase biomass.
Abstract: Contents. Preface. Acknowledgements. 1 Ecology and ecosystems. 1.1 Introduction. 1.2 Distribution and abundance. 1.2.1 Unit stocks. 1.2.2 Spacing of organisms. 1.3 Population growth and regulation. 1.3.1 Population growth. 1.3.2 Population regulation. 1.3.3 Life history patterns. 1.4 Marine ecosystems. 1.4.1 Coastal waters. 1.4.2 Coral reefs and lagoons. 1.4.3 Continental shelves and the open sea. 1.5 Human impacts on marine ecosystems. 1.5.1 Habitat modification and loss. 1.5.2 Eutrophication, siltation and heat. 1.5.3 Petroleum, toxic chemicals and solid waste. 1.5.4 Species invasions, introductions, and translocations. 1.5.5 Climate change - the greenhouse effect and global warming. 1.5.6 Ozone depletion. 1.5.7 Assessing and minimizing environmental impacts. 1.6 Photosynthetic marine organisms. 1.6.1 Macroalgae - seaweed. 1.6.2 Microalgae - phytoplankton. 1.6.3 Harmful algal blooms. 1.7 The flow of energy and material. 1.7.1 Zooplankton. 1.7.2 Daily migrations and the seasonal distribution of plankton. 1.7.3 Food relationships, trophic levels and foodwebs. 1.8 Productivity and fisheries. 1.8.1 Primary productivity and yield. 1.8.2 Productivity from fisheries and aquaculture. . 2 Exploited species. 2.1 Introduction. 2.2 Invertebrates. 2.2.1 Molluscs. Bivalves - clams and cockles. Gastropods - sea snails. Cephalopods - squids and octopuses. Management measures. 2.2.2 Crustaceans. Penaeids and carideans - prawns and shrimps. Nephropidae - clawed lobsters. Palinuridae - slipper and spiny lobsters. Brachyuran crabs. Anomuran crabs. Management measures. 2.2.3 Other invertebrates. Holothurians - sea cucumbers. Echinoids - sea urchins. Management measures. 2.3 Fishes. 2.3.1 Demersal fishes of cooler waters - cods, hakes and haddocks. 2.3.2 Demersal and reef fishes of warmer waters. 2.3.3 Coastal pelagic fishes - clupeoids. 2.3.4 Offshore pelagic fishes - tunas and sharks. 2.3.5 Management measures. 3 Fishing and fishers. 3.1 Introduction. 3.2 Fishing gear and methods. 3.2.1 Gleaning, spears and traps. 3.2.2 Hooks and lines. 3.2.3 Stationary nets. 3.2.4 Towed nets and dredges. 3.3 Fishers. 3.3.1 Fishing for food. 3.3.2 Fishing for income. 3.3.3 Fishing for recreation. 3.4 Effects of fishing. 3.4.1 Effects on target species. 3.4.2 Effects on non-target species. 3.4.3 Effects on the environment and ecosystems. . 4 Stock structure and abundance. 4.1 Introduction. 4.2 Structure and abundance. 4.2.1 Relative abundance. 4.2.2 Sampling surveys. 4.2.3 Mark-recapture methods. 4.2.4 Depletion methods. 4.3 Factors that increase biomass. 4.3.1 Size and growth. 4.3.2 Growth from length-frequency data. 4.3.3 Growth from tagging information. 4.3.4 Growth from hard-part analyses. 4.3.5 Reproduction. 4.3.6 Recruitment. 4.4 Factors that decrease biomass. 4.4.1 Age-based catch curves. 4.4.2 Length-based catch curves. 4.4.3 Mortality from mark-recapture data. 4.4.4 Natural mortality. 5 Stock assessment. 5.1 Introduction. 5.2 Stock abundance and catches - dynamic production models. 5.2.1 Equilibrium models. 5.2.2 Non-equilibrium models. 5.2.3 Multispecies applications. 5.2.4 Potential yield - rough estimators. 5.3 Including growth and mortality. 5.3.1 The effects of growth and mortality on biomass. 5.3.2 The effects of fishing mortality on a single cohort. 5.4 Including different year classes age-structured models. 5.4.1 Virtual population analysis. 5.4.2 The classical yield per recruit model. 5.4.3 The Thompson and Bell model. 5.5 Simulation and ecosystem models. 5.5.1 A biomass dynamic simulation model. 5.5.2 An age-structured simulation model. 5.5.3 Ecosystem models. 5.5.4 Risk assessment. 6 Fisheries management. 6.1 Introduction. 6.2 The need for fisheries management. 6.2.1 Biological overfishing. 6.2.2 Economic overfishing. 6.3 Managers and stakeholders. 6.3.1 Fisheries management authorities. 6.3.2 Co-management in commercial fisheries. 6.3.3 Community-based fisheries management. 6.4 The management process. 6.4.1 Management policies and objectives. 6.4.3 Reference points and indicators. 6.4.4 Management plans. 6.5 Management actions. 6.5.1 Input controls (on fishing and fishing effort). Limiting the number of fishing units. Limiting the efficiency and types of fishing gear. Minimum mesh sizes and escape gaps. 6.5.2 Output controls (on the catch). Quotas. Size limits. Rejection of females or gravid females. 6.5.3 Controls to protect the ecosystem. Closures as fisheries management tools. 6.5.4 Compliance and enforcement. References. Appendices. 1. Fisheries symbols and formulae. 2. Standard deviation and confidence limits. 3. Correlation and regression. 4. Least squares. 5. Collection of length-frequency data. 6. Bhattacharya plots. 7. Statistical tables. Glossary of terms. Index
1,350 citations
TL;DR: In this paper, the effects of fisheries on the associated biological systems are reviewed and management options and their inherent risks are considered, including the designation of marine protected areas, risk aversion, and the burden of proof.
Abstract: 1Some effects of fisheries on the associated biological systems are reviewed and management options and their inherent risks are considered.
2In addition to the effects on target species, other sensitive groups impacted by fishing are considered including marine mammals, turtles, sea birds, elasmobranchs and some invertebrates with low reproductive rates.
3Other impacts discussed include the destruction of benthic habitat, the provision of unnatural sources of food and the generation of debris.
4Management options are considered including the designation of marine protected areas, risk aversion, and the burden of proof.
5A balanced consideration of the risks and consequences of ‚Type 1’ and ‚Type II’ errors is advocated.
795 citations
TL;DR: It is concluded that immediate and delayed mortalities can occur in fish escaping from fishing gears and that the high variation in mortality rates within experiments is associated with a lack of information on how fish condition is affected by various fishing stressors and the type and severity of physical damage received.
243 citations
TL;DR: In this article, the authors examined vessel efficiency using a stochastic production frontier based on a sample of sea scallop vessels operating in the Mid-Atlantic between 1987 and 1990.
Abstract: Despite the extensive effort to research issues of allocative efficiency in fisheries, little empirical analysis of technical efficiency (TE) in fisheries exists. This study examines vessel efficiency using a stochastic production frontier based on a sample of sea scallop vessels operating in the Mid-Atlantic between 1987 and 1990. Estimates of TE are computed and compared with input usage, resource conditions, economic performance, and recently imposed regulations. The analysis suggests that owners and captains only partially compensate for changes in resource conditions through the use of labor and fishing effort, and recent regulations may improve overall TE in the short run.
207 citations
TL;DR: In this article, the authors describe the changes that have occurred in the fishery since the introduction of individual vessel quotas in 1991, based on the findings of two surveys, including interviews with most of the major halibut processors in British Columbia.
Abstract: Implementation of individual vessel quotas (IVQs) in the British Columbia halibut fishery has provided a unique opportunity to examine the effects of this management technique on a previously intense "derby" fishery. This paper describes the changes that have occurred in the fishery since the introduction of individual vessel quotas in 1991. The results presented here are largely based on the findings of two surveys. In September 1993, we conducted in-depth interviews with most of the major halibut processors in British Columbia. These processors reported significant changes in the processing and marketing of halibut. In Spring 1994, we conducted a mail survey of all 435 licensed halibut fishermen. The survey consisted of several series of questions designed to measure changes in fishing operations (crew size, fishing practices, etc.), quota leasing activities, changes in fishing income, and opinions about the effects of IVQs. The results presented here provide important information about the effects of t...
195 citations
TL;DR: The findings of this study suggest that the intensive differential cropping of top predators will not necessarily lead to increases in the biomass and productivity of their prey.
Abstract: A fishery independent underwater visual census technique was used to assess the effects of fishing on the diversity, biomass and trophic structure of the diurnally active non-cryptic reef-associated fish communities of the Seychelles. One hundred and thirty four species associated with three significantly different types of reef habitat were censused at one unfished ground and in six fishing grounds subject to different fishing intensities. There was in inverse relationship between fishing intensity and the biomass of several species targeted by the fishery. The diversity of families containing target species (lutjanidae, lethrinidae) was significantly higher at unfished and lightly fished sites as was the total biomass of the fish community and the biomass of piscivorous, piscivorous/invertebrate feeding and herbivorous trophic groups. However, there was no indication that the biomass of non-target species increased in response to the removal of their predators by fishing. The findings of this study are significant for fishery managers because they suggest that the intensive differential cropping of top predators will not necessarily lead to increases in the biomass and productivity of their prey.
177 citations
TL;DR: An aggregated energy-based coral reef simulation model was developed and used to perform fishing experiments where fishing intensity and catch selection were varied, indicating that fishing affects the coral reef's ecology and the benefits of the fisheries yield must be weighted against impacts on reef structure and processes.
173 citations
01 Jan 1995
TL;DR: In this paper, a review of the state of world fishery resources, globally, by region and species groups, as well as a brief account of environmental impacts on fisheries is presented.
Abstract: Following an earlier analysis provided by FAO (19931, the paper gives an update of the trends and future perspectives of world fisheries. It describes and comments on worldwide trends in landings, trade, prices and fleet size. It illustrates the decrease in landings in the last 3 years, the relationship between landings and prices and the large overcapacity in world fishing fleets. It provides a review of the state of world fishery resources, globally, by region and species groups, as well as a brief account of environmental impacts on fisheries. It presents an economic perspective for world fisheries which underlines further the overcapacity and subsidy issues that characterize modern fisheries. In conclusion, it discusses‘management issues including the need for fleet reduction policies, the potential combined effect of international trade on resources depletion in developing exporting countries, throwing into question the overall sustainability of the world fishery system.
168 citations
TL;DR: The main problems are caused by engineering works, industrial and domestic pollution, acidification, fishing and fishery management, and land use practices as discussed by the authors, and the major conservation objective must be habitat restoration and management, but short-term programs can usefully involve translocations, captive breeding and cryopreservation.
152 citations
TL;DR: A metapopulation model is investigated to see how marine reserves might help to conserve such populations and benefit fisheries, and it is shown that reserves become highly beneficial as the local extinction rate caused by fishing becomes large because they provide a source of recruitment into fished-out patches.
150 citations
TL;DR: In this article, a multispecies trophic model was proposed to predict sustainable yields of introduced fish species in African lakes, including the Nile perch fishery in Lake Victoria.
Abstract: Contributors. Series Foreword. Preface. General Introduction. Species change and fisheries in African Lakes: outline of the issues. Part One:- introduced Nile perch in Lake Victoria: Impacts on biodiversity and evaluation of the fishery: Impact of environmental change, species introductions and ecological interactions on the fish stocks of Lake Victoria. Limnological changes in Lake Victoria since the Nile perch introduction. Impact of fish species introductions on the tilapias of Lake Victoria and Kyoga. Diversity and stability of fish stocks in Lake Victoria, Kyoga and Nabugabo after establishment of introduced species. Dynamics of the haplochromine cichlid fauna and other ecological changes in the Mwanza Gulf of Lake Victoria. An analysis of species change in Lake Victoria: did the Nile perch act alone?. Analysis of species change in Lake Victoria using ECOPATH, a multispecies trophic model. Assessment of the Nile perch fishery in Lake Victoria. Thirty years on: the development of the Nile perch fishery in Lake Victoria. Socio-economic impacts of introduced species in Lake Victoria fisheries. Part Two:- evaluation of species change in other African lakes with introduced fish species: Inshore fish population and species changes in Lake Kariba, Zimbabwe. The impact of an introduction of sardine into Lake Kivu. The persistence of two introduced tilapia species in Lake Naivasha, Kenya, in the face of environmental variability and fishing pressure. Species change in reservoir fisheries following impoundment: the case of Lake Itezhi-tezhi, Zambia. Part Three:- evaluation of species changes in African lakes without introduced species: Changes in species composition and abundance of fish populations in Lake Turkana, Kenya. Management, conservation and species changes of exploited fish stocks in Lake Malawi. Changes in demersal cichlid communities as a result of trawling in southern Lake Malawi. Changes in species composition and abundance as a consequence of fishing in Lake Malombe, Malawi. Effects of exploitation on the pelagic fish community in the south of Lake Tanganyika. Changes in the pelagic fisheries of northern Lake Tanganyika during the 1980s. Part Four:- overviews of fish introductions in African Lakes: Genetic impacts of fish introductions: a perspective on African lakes. Fish introductions in the African Greak Lakes: some special characteristics. Thinking th unthinkable: a candidate model for predicting sustainable yields of introduced fish species in African lakes. Why is Limnothrissa miodon such a successful introduced species and is there anywhere else we should put it? Appendix: summary of characteristics of major African lakes. Author index. Species index. Subject index.
TL;DR: In this paper, a model using a household production framework to link measures of nonpoint source pollution to fishing quality and a random utility model to describe how that quality influenced sport fishing parties' decisions in North Carolina.
Abstract: In this paper we describe a model using a household production framework to link measures of nonpoint source pollution to fishing quality and a random utility model to describe how that quality influences sport fishing parties' decisions in North Carolina The results provide clear support for using a model that evaluates the effects of pollution on the activities and decisions associated with the fishing activity once a trip is taken Site selection decisions are then conditioned on the anticipated quality of fishing sites The framework also has the advantage of linking the spatial, technical, and economic information required to evaluate the management plans required for estuaries under the National Estuarine Program
TL;DR: A review of the empirical literature on the economic value of marine recreation fishing, beach visits, and boating can be found in this paper, where the authors investigate the relationship between pollution control policy and the attributes of the activity that people value (catch rate).
Abstract: This paper reviews the empirical literature on the economic value of marine recreation fishing, beach visits, and boating Questions addressed include: What values do people place on changes in the attributes of recreation sites and activities? What do we know about how water pollution control policy affects these attributes? And, is it feasible to use the value information obtained for specific sites and/or activities to estimate the benefits of improving marine water quality? The literature establishes that some measures of pollution reduce the values of trips to beaches and that improved fishing success is valued by recreational anglers However, there is substantial variation in value measures across studies Welfare estimates can be sensitive to model specification and estimation In the case of marine recreational fishing, the links between pollution control policy and the attributes of the activity that people value (catch rate) have not been established
TL;DR: Improvement of the situation demands stricter management of riverine systems through the protection of the few that remain in a relatively pristine state, and those modified should be restored if social, political and economic conditions allow.
Abstract: Human use of river systems has intensified considerably in the last century due to increasing population and the associated higher demand for water through industrial and agricultural technologies. This intensification process has impacted rivers and resident organisms. Natural rivers have rich and varied fish faunas adapted to the variable climate and morphology of such systems. Much of the diversity and resilience can be traced to the connectivity between two very different components, the channel and the floodplain. Fisheries in rivers are as diverse as the fish communities and are adjusted for capturing most species and life stages throughout the year. Fisheries reasonably conducted have proved sustainable with a high rate of catch correlated with the intensity of flooding in the same or preceding years. Fish communities react in a predictable manner to externally imposed stresses, whether eutrophication, induced by humans or natural environmental modification, or fishing, through successive loss of large species and their replacement by smaller, faster growing species. Generally, the overall weight of catch remains little affected by this process until excessive levels of exploitation are reached and the stock collapses. Damage to fish communities through overfishing and environmental modification is widespread. Improvement of the situation demands stricter management of riverine systems through the protection of the few that remain in a relatively pristine state, and those modified should be restored if social, political and economic conditions allow. Should this not be possible, approaches to the mitigation of externally imposed stresses should be sought and applied.
TL;DR: In this paper, the authors compared the Mediterranean fish communities of two rocky coastal areas, one inside an integral marine reserve and the second outside the reserve, near Banyuls-sur-Mer, France, using underwater visual census after a 12-year interval.
TL;DR: Research into bycatch in Australia has concentrated on attempts to describe and quantify the highly variable but very large quantities and diversities of bycatches from prawn trawling, showing the great potential that more selective trawl gears have for alleviating the chief problems concerning demersal trawl bycatch.
Abstract: A common definition of the term ‘bycatch’ is that part of the gross catch which is captured incidentally to the species towards which there is directed effort. Under such a definition, there are few fisheries in Australia (nor the world) which do not have bycatch, making the scope, diversity and history of the issue enormous. In recent years, the majority of interest in bycatch has focused on demersal trawl fisheries because conventional otter trawls are comparatively non-selective fishing gears and so catch large quantities of a wide range of untargeted species.
TL;DR: The highest documented incidence of wildlife entanglement by fishing debris is for the Australian fur seal in Bass Strait and off southern Tasmania, where over the period 1989–1993 approximately 1.5-2% of seals were found with neck collars.
01 Jan 1995
TL;DR: In this paper, the authors present a review of the deep-water fish assemblage in the North Atlantic and compare the performance of trawling and longline research in the Davis Straits.
Abstract: Preface. Introduction. 1: Scientific papers. Environmental and biological aspects of slope dwelling fishes of the North Atlantic J.D.M. Gordon, et al. Structure over time of an exploited deep-water fish assemblage R.L. Haedrich. The biology and fishery of roundnose grenadier (Coryphaenoides rupestris, Gunnerus, 1765) in the North West Atlantic D.B. Atkinson. Greenland halibut (Reinhardtius hippoglossoides): A review of the dynamics of its distribution and fisheries off eastern Canada and Greenland W.R. Bowering, W.B. Brodie. The distribution, relative abundance and the biology of the deep-sea fishes of the icelandic slope and Reykjanes ridge J.V. Magnusson, J. Magnusson. Deep-water resources in Faroese waters to the south, southwest and west of the Faroes - a preliminary account J. Reinert. Comparisons between longlining and trawling for deep-water species - selectivity, quality and catchability - a review N.R. Hareide. A comparison of deep-water trawl and longline research fishing in the Davis Straits G.A. Jorgensen. Experience with management of orange roughy (Hoplostethus atlanticus) in New Zealand, and the effects of commercial fishing on stocks over the period 1980-1993 M. Clark. Age determination of deep-water fishes experiences, status and challenges for the future O.A. Bergstad. 2: Review papers. Spanish North Atlantic deep-water fisheries S. Iglesias, J. Paz. The Irish experience of deep-water fishing in the North East Atlantic R. McCormick. Fisheries policy and the survival of fishing communities in eastern Canada R.E. Ommer. Line fishing for black scabbard fish (Aphanopus carbo, Lowe, 1839) and other deep-water species in the eastern mid-Atlantic to the north of Madeira R.Martins, C. Ferreira. French exploration of the deep-water fisheries of the North Atlantic A. Charuau, et al. Russian (USSR) fisheries research in deep waters (below 500 m) in the North Atlantic F.M. Troyanovsky, S.F. Losovsky. Norwegian experience of deep-water fishing with longlines H.E. Olsen. 3: Technical papers. Experimental utilisation and marketing of by-catches and deep-water species in Ireland H.P. Thorsteinsson, G. Valdimarsson. Deep-water trawling techniques used by Icelandic fishermen G. Gunnarsson. Canadian experience: deep-water fishing gill netting in the Northwest Atlantic Ocean A. Duthie, A. Marsden. 4: Summary of workshop sessions. Appendix: List of delegates and the steering committee.
TL;DR: A geographically distinct, Antarctic, open-ocean food chain which is of importance to air breathing predator species but where Antarctic krill, Euphausia superba, is absent is identified.
Abstract: Recent data from research cruises and explorator fishing in the Antarctic Polar Frontal Zone (APFZ) of the Scotia Sea, together with data from dietary studies of Antarctic vertebrate predators, have revealed a large, previously overlooked trophic system in the Southern Ocean (Fig. 1). The upper trophic levels of this open-ocean epipelagic community are exceptional in that they contain no fish species. Fishes are replaced by cephalopods, including the ommastrephid squid, Martialia hyadesi. This squid preys on mesopelagic m.yctophids (lanternfish), which feed largely on copepods. We identify here a geographically distinct, Antarctic, open-ocean food chain which is of importance to air breathing predator species but where Antarctic krill, Euphausia superba, is absent. This system is probably prevalent in areas of higher primary productivity, especially the Scotia Sea and near the peri-Antarctic islands. Squid stocks in the APFZ may have potential for commercial exploitation, but they, and the predators they support, are likely to be sensitive to overfishing. Squid have a short, semelparous lifecycle, so overfishing in a single year can cause a stock to collapse.
TL;DR: A discrete, space-time, age-structured model of a fishery was developed to test the effect of marine reserves on yield of fish to recreational angling and appeared to be optimal for blacktail.
Abstract: A discrete, space-time, age-structured model of a fishery was developed to test the effect of marine reserves on yield of fish to recreational angling. The model was applied to three sympatric surf-zone species commonly targeted by shore-anglers. Movement rates of white steenbras Lithognathus lithognathus and galjoen Dichistius capensis, both of which are nomadic, were estimated from tag-recovery data. Because post-recruit blacktail Diplodus Sargus capensis are resident, a coefficient of passive larval diffusion was estimated from drogue-separation rates. Marine reserves cannot increase the yield-per-recruit of white steenbras, although the spawner-biomass-per-recruit responds positively. A "recruitment - spawner-biomass" function was applied to galjoen and blacktail. The yield of galjoen increased sharply as the size of area conserved increased. Small reserves, closely spaced, appeared to be optimal for blacktail. A range of reserve size and spacing combinations satisfied management criteria for the thre...
TL;DR: A statistical model is constructed to test the hypothesis that the collapse of the northern Atlantic cod fishery was caused by an increase in natural mortality in the first half of 1991 and suggests that overfishing was sufficiently high in recent years to support this hypothesis.
Abstract: The collapse of the northern Atlantic cod (Gadus morhua) fishery off southern Labrador and to the northern Grand Bank of Newfoundland, once the largest cod fishery in the world, was a social and ec...
TL;DR: The development of Japan's community-based fishery management system is described in this article, where three fishery laws were in effect over the past 250 years, and each of them commonly adopted a fishing rights system as a tool for coastal fisheries management.
Abstract: The development of Japan's community-based fishery management system is described. Over the past 250 years, three fishery laws were in effect. These fishery laws commonly adopted a fishing rights system as a tool for coastal fisheries management. During the feudal era until 1867, the fishing right system was used mainly to collect a fishery tax. The fishing right system established by the Old Fishery Law (1901-1947) helped to reduce conflicts between fishermen exploiting the same resources with different gears. The Current Fishery Law, enacted in 1949, has led to "Territorial Use Rights in Fisheries" by limiting its coverage to sedentary resources and non-mobile gear. At the same time, the Current Fishery Law created a system to establish coastal fishery management plans through fishing rights and licenses. These innovations have motivated fishermen to create the community-based coastal fisheries management system. Since the inception of the Current Fishery Law in 1949, the number of fishery management or...
Journal Article•
TL;DR: For a large water system where social fishing is the rule, a minimum colony size of c. 1000 pairs is required as discussed by the authors, which is considered a breakpoint for this kind of behaviour.
Abstract: The habit of mass fishing by Cormorants at lake IJsselmeer, The Netherlands, is a recent phenomenon. During the first half of the 1970s the birds changed behaviour probably as a result of the deteriorating under water visibility in the lake (3-4 m water depth). The behavioural switch coincided with years of high numbers of Smelt Osmerus eperlanus and Ruffe Gymnocephalus cernuus present in the southeastern part of lake Markermeer, the birds' main fishing area at that time. Social fishing by Cormorants is directed towards the catch of relatively small, pelagically dwelling fish. It is argued that for a large water system where social fishing is the rule, a minimum colony size of c. 1000 pairs is required. Typically each colony had one socially fishing group (4000-5000 birds) that slowly changed position through the course of the day. Depending on the direction of the wind the flock's position could greatly change between days. Hunting speed was measured and coincided with maximum swimming speed of medium sized fish prey (15-25 cm). Hunting speed increased during the season probably as a result of the greater swimming speeds of the fish at higher temperatures. Intake rate was closely linked to the birds' position within the flock indicating local depletion of the fished water layer. Mass fishing was especially rewarding at intermediate light intensities under water (50-80 cm Secchi depth, or 300-500 mu E.m(-2)s(-1) at 40 cm depth). The habit of pushing up the fish against the light back-ground of the clear top water layer was only possible when wind caused no greater turbidity than 40 cm Secchi depth (100 mu E.m(-2)s(-1)) which is considered a breakpoint for this kind of behaviour. Adapting the habit of mass fishing effectively enabled the birds to exploit the turbid, rapidly changing environment which resulted in the extension of the foraging range thus maximising colony size relative to the resources available.
TL;DR: The size and composition of finfish yield from six Fijian reef fisheries was determined using catch records from a voluntary logbook scheme and it suggested that the fisheries examined were all capable of sustaining the reported yields and that in sites where yields were less they might be increased sustainably.
Abstract: The size and composition of finfish yield from six Fijian reef fisheries was determined using catch records from a voluntary logbook scheme. A total of 172 logbooks were issued for 30-day periods in October 1992 and February and June 1993 and they provided information on 1369 fishing trips. Catch records were weighted, using the results of contemporaneous fishing activity and fleet size surveys, to provide yield estimates for each fishing ground (qoliqoli). Yield from all qoliqoli was dominated by Serranidae and Lethrinidae which were favoured for consumption and sale. Yields were expressed on the basis of reef area for fish from different trophic groups. Macroinvertebrate-feeders and piscivores accounted for more than half the yield in all qoliqoli and there were significant differences in area specific yield between qoliqoli. There was no evidence of fishers adopting more powerful fishing techniques or catching fish from lower trophic levels in order to maintain yield from any qoliqoli. This suggested that the fisheries examined were all capable of sustaining the reported yields of up to 3.4 tonne km−2qoliqoli year −1 or 10.2 tonne km−2 coral reef year −1 and that in sites where yields were less they might be increased sustainably.
TL;DR: In this paper, the use of aquatic resources by five fishing communities on the Atlantic Forest coast of southeast Brazil: Buzios Island, Puruba, and Picinguaba in Sao Paulo State, and Jaguanum and Itacuruca Islands at Sepetiba Bay in Rio de Janeiro State.
Abstract: Recent work has dealt with the local management of aquatic resources as an alternative to Hardin's (1968) “tragedy of the commons.” In communities with no formal management of resources, informal ownership of fishing spots or conflicts with outside competitors may determine the basis for future local management. In this study, I analyze the use of aquatic resources by five fishing communities on the Atlantic Forest coast of southeast Brazil: Buzios Island, Puruba, and Picinguaba in Sao Paulo State, and Jaguanum and Itacuruca Islands at Sepetiba Bay in Rio de Janeiro State. Informal ownership of fishing spots, used for set gillnet fishing, is regulated by kin ties at Buzios Island. The artisanal fishers of Sepetiba Bay, especially those from Jaguanum Island, have a conflict with Bay “intruders,” such as the shrimp and herring trawlers. Two coastal communities, Puruba and Picinguaba, have conflicts with fishing regulations from a State Park (Parque Estadual da Serra do Mar),created in 1977. The transformation of populated areas of the Atlantic Forest to Extractive Reserves might be a way to avoid conflicts with intruders and with governmental agencies, and to involve local populations in management. Kinship rules at Buzios Island and the territorial behavior of fishers at Sepetiba Bay may form a basis for local organization.
TL;DR: In this paper, the authors evaluated the loss of unique fish assemblages in Minnesota lakes by comparing species presence in historical and most recent surveys of both stocked and unstocked lakes.
Abstract: The loss of unique fish assemblages in Minnesota lakes was evaluated by comparing species presence in historical and most-recent surveys of both stocked and unstocked lakes. Fish stocking resulted in greater species richness but reduced fish assemblage diversity among stocked lakes. No significant changes occurred among unstocked lakes. Short-term goals of additional fishing opportunities were partially achieved through stocking by creating more opportunities to fish for walleye in more lakes. However, the resulting loss of fish assemblage diversity within a local management area was apparently not considered. Fisheries managers should consider the potential for loss of community diversity and preserve unique fish communities where they still exist.
TL;DR: In this article, fish catches from the coral reefs of the Tulear region (southwest Madagascar) are analyzed based on fish landings. And the results appear to be representative of the artisanal fishery catches in the southwest Indian Ocean.
Abstract: Fish catches from the coral reefs of the Tulear region (southwest Madagascar), are analyzed based on fish landings. This region of the island consists of two barrier reefs, two coral banks, three lagoon reefs and a fringing reef. The total reef area studied was 190 km2. Of the whole fishing area, the reef flat was the most frequently used by fishermen. Line catches per unit effort (CPUE) were stable throughout the eight month sampling period (6 to 8 kg/trip to sea), whereas gillnet and seine catches showed differences between the cold period and the warm period. These results appear to be representative of the artisanal fishery catches in the southwest Indian Ocean. Annual fish yield was estimated at 12 t km−2 yr−1. Comparable yields have been recorded in certain regions of the Indo-Pacific, that have similar ratios of coral reef area to adjacent shallows and similar fishing practices. Reef species (Lethrinidae, Siganidae) dominated the catches. At present, coastal waters of the Tulear region are heavily fished, and the fishermen report a progressive decrease in the average size of fish caught over the last 15 years. Management measures are suggested, based on preliminary findings.
TL;DR: The Barents Sea/Norwegian Sea ecosystem is inhabited by two large pelagic fish stocks, the Norwegian spring spawning herring and the Berns Sea capelin this article.
Abstract: The Barents Sea/Norwegian Sea ecosystem is inhabited by two large pelagic fish stocks, the Norwegian spring spawning herring and the Barents Sea capelin. The herring stock feeds in the high-production polar front area in the western Norwegian Sea, and spawns at the Norwegian coast. The larvae are transported into the Barents Sea, where they spend the first two to four years of life. The capelin stock spends its whole life in the Barents Sea, spawning along the southern coasts and feeding in the nutrient-rich areas in the northern parts of the sea. The herring stock was brought almost to extinction during the 1960s by the combined effect of overfishing and environmental conditions. This stock is now recovering. Much fishing effort was shifted to capelin when the herring fishery was stopped, and the capelin supported large fisheries in the 1970s. In the mid 1980s, the capelin stock size suddenly declined to a very low level. The factors involved were recruitment failure, low individual growth rates, high natural mortality, and, in the last phase, high fishing mortality. The recruitment failure was most likely caused by predation by some abundant year classes of herring in 1983-85. The low growth rate was probably caused by the scarcity of prey organisms, while the high mortality rate of the adult capelin stock was an effect of predation from abundant year classes of cod during the same period. After having recovered in the period 1989-91, the capelin stock once more collapsed during 1992-93. The reasons were the same as for the collapse in the 1980s, except that fishing had no effect on the most recent collapse. Key words: Barents Sea, ecology, fisheries, capelin, herring, polar cod
Journal Article•
TL;DR: The complementary relationship of recruitment to spawning stock shows that fishing effort two years prior to spawning, i.e., on the recruits to the fishery, is significant in explaining the decline in coastal spawning stock.
Abstract: Previous studies have shown that environmental factors, the Lecuwin Current and westerly winds, have a significant effect on levels of puerulus settlement at coastal locations in the western rock lobster (Panulirus cygnus) fishery. However, these environmental factors do not explain an average decrease of 50% in the puerulus settlement at the Abrolhos Is. (on the edge of the continental shelf, 60 km off-shore from the north coastal region) from the 1970s compared with that observed in the last 9 years. During the past 20 years there has been an increase in fishing effort resulting in a marked decline in the spawning stock, particularly in the north coastal region. The stock-recruitment-environment relationships for three sites covering the main regions of the fishery show that environmental effects explain the main fluctuations in puerulus settlement in the coastal sites, Dongara and Alkimos, with the spawning stock not being significant. However, the reduction in spawning stock appears to be the main factor explaining the decline in Abrolhos Is. settlement during the last 9 years. The complementary relationship of recruitment to spawning stock shows that fishing effort two years prior to spawning, i.e., on the recruits to the fishery, is significant in explaining the decline in coastal spawning stock.